Contraception: the combined pill
How does it work?
The combined oral contraceptive pill contains synthetically produced oestrogen and progestogen. These synthetic hormones imitate the natural ones produced by women every month. The pill works by:
- preventing the release of eggs from the ovaries;
- changing the lining of the womb to make it hostile to a fertilised egg which is trying to implant; and
- thickening cervical mucus to form a barrier to sperm so that they can’t swim up into the uterus and fallopian tubes.
How effective is it?
The combined oral contraceptive pill is about 99 per cent effective when taken as directed.
What are the advantages?
Some of the advantages of the pill are that it:
- is extremely effective and reliable;
- can reduce the risk of ovarian cancer by 40 per cent;
- can reduce the risk of cancer of the uterus (womb) by 50 per cent;
- can reduce the incidence of pelvic inflammatory disease;
- may decrease premenstrual syndrome, acne, bleeding, anaemia and risk of ovarian cysts;
- may result in periods becoming shorter, lighter, less painful and more regular;
- usually allows fertility to return within 6 months of stopping it; and
- rarely has serious side effects.
What are the disadvantages?
Some of the disadvantages of the pill are that it:
- is only available on prescription;
- does not protect against sexually transmitted diseases;
- cannot be used by women who have had breast cancer, a stroke, heart attack, deep vein thrombosis, blood clots, liver disease, kidney disease, or unexplained vaginal bleeding, smokers aged over 35 and those on certain medications;
- should not be used by those with high blood pressure, diabetes, migraine headaches, depression or certain blood disorders such as sickle cell anaemia;
- should not be used during breast feeding, as the oestrogen can suppress lactation;
- can cause side effects such as nausea, breast tenderness, mid-cycle bleeding for the first few months, weight gain, fluid retention, headaches and irregular skin pigmentation on the face (particularly if exposed to the sun); and
- can, in rare instances, cause serious side effects such as blood clots, stroke, heart attack, high blood pressure and liver and gallbladder disease.
How is it used?
The combined pill is taken daily for 21 days, and then no pills, or, dummy pills without any hormones, are taken for 7 days to complete the 28-day cycle. You will have your period during the 7-day break without hormones.
Combined oral contraceptives may be:
- monophasic (where each active pill has the same dose of oestrogen and progestogen);
- biphasic (where the dose of oestrogen is constant, but the dose of progestogen is increased for the second half of the cycle); or
- triphasic (where the oestrogen is increased mid-cycle, and the progestogen is progressively increased throughout the 3 active phases of the cycle).
You should start your first pill when you have a period, carefully following the instructions that come with the packaging. This should include taking the pill at about the same time every day. You should not rely on the effectiveness of the pill alone for the first 7 days of the first packet, so use a condom as well during this time. You should also use a barrier method if you miss a pill, if you experience vomiting or diarrhoea, or if you are prescribed a course of antibiotics.
The pill should also be discontinued for 4-6 weeks before any elective surgery associated with an increased risk of blood clotting. Talk to your doctor, who may be able to prescribe the mini-pill instead for this time.
Last Reviewed: 01 May 2002
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